Cations heterocyclic

When an exocycllc function has a higher priority, it may be necessary to name a cationic heterocyclic substituent group. The most important case is that in which the heterocyclic substituent is bonded through its cationic center. Such cases may be named in two ways, as in (182) and (183). The simplest is to use the suffix -io , as used for the H3N— substituent, ammonio terminal e is elided. More generally, however, an -yl suffix is appended after -I um , as shown in the second names given for the examples. This method applies equally well to situations with other sites of attachment, and also allows one to name divalent substituents, e.g. (184) and (185). 

Although 1,3,2-diazaphospholenium cations are usually prepared from neutral NHPs or 1,3,2-diazaphospholes via Lewis-acid induced substituent abstraction or A-alkylation, respectively (cf. Sect. 3.1.2), the group of Cowley was the first to describe a direct conversion of a-diimines into cationic heterocycles by means of a reaction that can be described as capture of a P(I) cation by diazabutadiene via [4+1] cycloaddition [31] (Scheme 4). The P(I) moiety is either generated by reduction of phosphorus trihalides with tin dichloride in the presence of the diimine [31] or, even more simply, by spontaneous disproportionation of phosphorus triiodide in the presence of the diimine [32], The reaction is of particular value as it provides a straightforward access to annulated heterocyclic ring systems. Thus, the tricyclic structure of 11 is readily assembled by addition of a P(I) moiety to an acenaphthene-diimine [31], and the pyrido-annulated cationic NHP 12 is generated by action of appropriate... 

Bunyapaiboonsri, T Ramstrom, H. Ramstrom, O. Haiech, J. Lehn, J.-M. Generation of bis-cationic heterocyclic inhibitors of Bacillus subtilis HPr kinase/phosphatase from a ditopic dynamic combinatorial library. J. Med. Chem. 2003,46, 5803-5811. 

The effects of substituent groups in the reactions of the cationic heterocycles with nucleophiles are entirely as expected. Appropriately situated substituent groups which can function as leaving groups can be displaced (e.g. equation 41), and ANRORC reactions are very common (e.g. equations 42 and 43). The latter type of reaction is of particular... 

In common with other cationic heterocycles, the charged ring enhances the reactivity of substituents on the ring. Thus these substituents will usually be resistant to electrophilic reagents, and be susceptible to reaction with bases or nucleophilic reagents. 

Heterocycles form a specific class of monomers. They do not usually undergo radical polymerization, and the kind of ionic polymerization mechanism is determined by the kind of heteroatom, substituent and ring size. Oxiranes and, aziridines are polymerized by both ionic mechanisms. With the exception of lactone, four-membered and larger heterocycles with oxygen and with substituted nitrogen can only be polymerized cationically heterocycles with unsubstituted nitrogen can also be polymerized anionically. 

Se chemical shifts span a wide range of ca. 3300 ppm the extremes are marked by selenoaldehydes, some molybdenum selenides, and cationic heterocycles (up to S = 2434) at the high-frequency end and bridging selenium (p) in tungsten complexes (3 = —900) at the low-frequency end. A detailed discussion of electronic influences on Se chemical shifts and its variation in different classes of compounds has been published. In the following, some general characteristic tendencies are collected. 

As expected, an aryl substituent is more readily substituted by electrophilic reagents than the cationic heterocyclic ring <61JA2934, 74CR(C)237>. 

The cationic heterocyclic aminals 45 are novel glycosylating agents. Compound 45 (R = H, X = Cl), treated with allyl 4,6-0-benzylidene-a-D-glucopyranoside, afforded 90% of the a-(l- 2)-linked kojibiose derivative. Tetra-O-benzyl-a-D-... 

Hutchison, G.R., MjV. Ratner, and T.J. Marks. 2005. Electronic structure and band gaps in cationic heterocyclic oligomers, midtidimensional analysis of the interplay of heteroatoms, substituents, molecular length, and charge on redox and transparency characteristics. J Phys Chem B 109 3126. 

Of the acyl hydrazones formed in this case, active lead compounds containing two terminal cationic heterocyclic recognition groups separated by a spacer of appropriate structure could be rapidly identified using a dynamic deconvolution procedure. 

Lu and Malinkova researched the regio- and diastereoselective insertion of allenes into stable oxapalladacycles giving 3,4-dihydro-2H-l-benzopyrans. The insertion of allenes into Pd-G bonds of cyclopalladated pyridine derivatives was studied giving novel cationic heterocycles (berberinium derivatives). ... 

Cordone R, Harman WD, Taube H. Carbon-hydrogen bond activation in novel f -bound cationic heterocycle complexes of pentaatnmineosmium(II). J Am Chem Soc. 1989 111 2896-2900. 

Cations s. a. Radical cations -, heterocyclic, review 22, 261 suppl. 27... 

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